The present invention relates to sliding window sash systems and, more particularly, to a balancing spring system for facilitating the manual opening and closing of window sashes.
Double hung and single hung windows known in the art comprise vertically translating window sashes. The window sashes slide in channels located alongside the window jambs of a window frame. Either sash can overlap the other sash to provide varying openings of the window. A window sash generally comprises, at its top end, a locking mechanism to engage the window sash in a stationary position along the window jambs.
Balancing spring systems have been provided to facilitate the opening and closing of window sashes. For instance, window sashes having large dimensions, thick glass or many layers of glass would be a handful to manually lift. Furthermore, such heavy window sashes would also be subject to the risk of forcefully sliding down the window jambs, possibly causing the shattering of the glass and endangering the people of the surrounding environment. Therefore, balancing spring systems known in the art provide spring mechanisms along window jambs to upwardly bias the window sash, such that only a small amount of force needs to be applied to the window sash for the lifting and opening thereof. Also, the window sash is kept in vertical balance within the channels of the window jambs by the spring mechanism. Similarly, only a small amount of force needs to be applied to the window sash for the closing thereof.
Curled ribbon springs have been used in balancing spring systems as they have the distinct advantage of providing a constant force, whereby the counterbalancing of the window sash is possible by opposing the constant force of such springs to the constant weight of the window sash. A curled ribbon spring consists in a spring ribbon curled around a reel, whereby the ribbon has been formed such that, when a free end portion thereof is extended and uncurled from the reel, that extended free end portion recurls itself around the reel. The recurling force of the curled ribbon spring is a function of the width thereof, amongst other factors.
U.S. Pat. No. 5,232,208, issued on Aug. 3, 1993 to Braid et al., discloses a frame tensioning arrangement, wherein a ribbon spring is curled to a reel. The curled ribbon spring is idle and free to rotate within a channel of a window jamb. A tongue at a free end of the curled ribbon spring is connected to a window sash shoe. The window sash shoe supports a window sash and comprises a pivoting mechanism enabling the latter to pivot outwardly of the window jambs. The window sash shoe is also slidably mounted in the channel of the window jamb, such that the window sash may move vertically. The curled ribbon spring applies an upward force on the window sash via the shoe, for facilitating the opening and the closing of the window sash.
If the amount of upward force required to counterbalance the window sash is greater than what can be provided by the curled ribbon spring in place, a few possibilities are at hand to increase the force thereof. As mentioned above, the width of the curled ribbon spring can be increased, but only to a certain extent as the available space within the channel is a limitation.
Because of the restricted space in the channels of the window jambs, curled ribbon springs have been added in series in window jamb channels rather than having an increase in width to enhance the biasing force thereof. The prior art system of the above referred-to patent discloses slots and indentations on the tongue of the free end of the first curled ribbon spring, whereby a second curled ribbon spring can be attached thereto, for the afore-mentioned purpose. Furthermore, the first and second curled ribbon springs are identical, whereby other curled ribbon springs can be added in series.
However, it is found that adding either slots or indentations weakens the ribbon spring. Furthermore, the area comprising the slots or indentations is subject to a greater stress as it serves as connections means and thus sustains the biasing forces of the added curled ribbon springs. This may result in the premature failure of the curled ribbon spring. In this case, the repair is a lengthy and inconvenient operation as it requires the removal of the window sash. Furthermore, as the ribbon springs are in series, the replacement of a broken ribbon spring may require the removal of the ribbon springs connected thereto, thereby extending the repair time.
It is also found that when using stacks of curled ribbon springs that are interconnected as shown in the above described prior art, the lowest curled ribbon spring does not require to be as long as the highest one. This involves keeping an inventory of different lengths of curled ribbon springs for one size of window sash.
It is a feature of the present invention to provide a balancing spring system for facilitating the manual opening and closing of window sashes and substantially overcoming the above mentioned disadvantages of the prior art.
According to the above feature of the present invention, from a broad aspect, the present invention provides a balancing spring system for facilitating the opening and the closing of a window sash assembly slidably mounted in channels of opposed window jambs. The balancing spring system comprises a connector strip having an elongated rectangular shape defining a front surface and a rear surface. The connector strip also has at least two slots formed therein. Each of the slots extends from the front surface to the rear surface. The connector strip has a connecting head section at a bottom end thereof, adapted for connection to a window sash. At least a first and a second curled ribbon spring are adapted to be mounted idle and free to rotate in one of the channels of the window jambs. The first and second curled ribbon spring each have a connecting free end section, for connecting the first and second curled ribbon spring to the slots of the connector strip, whereby the first and second curled ribbon springs apply an upward force to the window sash assembly.
According to a further broad aspect of the present invention there is provided a connector strip adapted for connecting a window sash assembly slidably mounted in channels of opposed window jambs to a biasing mechanism applying an upward force to the window sash assembly. The connector strip has an elongated rectangular shape defining a front surface and a rear surface and at least two slots therein. Each of the slots extends from the front surface to the rear surface and is adapted for connecting the connector strip to the biasing mechanism. The connector strip has a connecting head section at a bottom thereof adapted for connecting the connector strip to the window sash assembly.